A superconducting accelerator that accelerates charged particles such as electrons or protons using a superconductive acceleration cavity is known. A superconducting accelerator makes a superconductive acceleration cavity, which is formed of a superconducting material, superconductive by cooling the superconductive acceleration cavity using a refrigerant such as liquid helium. Accordingly, the electrical resistance of the superconductive acceleration cavity becomes almost zero and thus charged particles can be efficiently accelerated without power loss.
In such a superconducting accelerator, a resonance frequency of the superconductive acceleration cavity is tuned by adjusting the length of a gap in which a high-frequency electric field for accelerating charged particles is formed in the superconductive acceleration cavity.
Patent Document 1 discloses a configuration in which the length in an axial direction of a refrigerant tank that accommodates a superconductive acceleration cavity is adjusted by changing the distance between two flanges which are disposed in the refrigerant tank. In this configuration, by providing a wedge-shaped nut having a tapered surface between seat plates which are in close contact with the two flanges and moving the nut along the surfaces of the seat plates using a bolt, a gap between the seat plates is adjusted.
A resonance frequency tuning method using beam members having a length larger than the diameter of the refrigerant tank and provided on both sides of the superconductive acceleration cavity in a diameter direction of the refrigerant tank has been proposed. Here, one end of one of the beam members is connected to that of the other of the beam members with a screw member attached to one side of the refrigerant tank in the diameter direction, also the other end of one of the beam members is connected to that of the other of the beam members with another screw member attached to the other side of the refrigerant tank. According to this method, by changing a gap between the beam members using the screw members, the superconductive acceleration cavity is deformed to change the length of a particle passage and it is thus possible to tune the resonance frequency of the superconductive acceleration cavity.